Volcanic Alert Bulletin WI-2013/11 - White Island Volcano

The main steam and gas plume is coming from the ash cone occupying the previous hot lake crater. The small lake to the north is the cool lake and the lava dome crater is partially hidden under the steam plume to the left of the cool lake.

Ash emission at White Island has ceased for the moment and the Volcano Alert Level is reduced to 1 with the Aviation Colour Code changing to Yellow.

Observations in the last week have shown that a small ash cone has been built in the “hot lake” crater, which is the current focus of activity. The ash cone is surrounded by a small moat of water.

It is likely that in the short term, activity will alternate between dry and wet eruptions. When drier conditions prevail, like last week, some volcanic ash may be produced. If there is an increase in water near the vent then phreatic (steam-driven) eruptions may occur. The crater containing the lava dome remains unchanged.

Seismic tremor levels are currently low, which is thought to partly reflect the lack of water involvement in the current activity. A gas flight on 26 February measured around 600 tonnes per day of SO2 (sulphur dioxide), and 1,950 tonnes per day of CO2 (carbon dioxide), similar to other measurements made since the start of 2013.

White Island remains in a heightened state of unrest and the long term outcome of the unrest remains unclear. It could lead to explosive eruptions and larger ash emissions, like in August 2012, or decline to background activity. In the short term it is expected that activity will be variable, largely reflecting the influence of water on the style of activity.

Background

Unrest at White Island began in July 2012, leading to explosive eruptions and ash emissions in August. A small lava extrusion occurred in November, followed by phreatic, steam driven activity in December which continued through January and February 2013. Minor ash emissions have been interspersed throughout this eruption sequence as conditions within the craters have changed.

The Volcanic Alert Level ranges from 0 to 5 and defines the current status at a volcano. Level 1 indicates signs of volcanic unrest.

Aviation Colour Codes are based on four colours and are intended for quick reference only in the international civil aviation community.